Conversion arrangement for optical units for use with cameras

ABSTRACT

A conversion arrangement for mounting optical units on a camera such as a film or television camera has a generally cylindrical mounting body (12, 14) for attachment to the camera body, a generally cylindrical carrier (B) for attachment to the optical unit, the carrier being coaxially coupled to the mounting body for axial movement relative to the mounting body, and a focusing ring (22) which is coaxial with and coupled to both the mounting body (12, 14) and the carrier (B). The focusing ring is rotatable relative to the mounting body and carrier to move the carrier axially of the mounting body to focus the optical unit. Backlash during focusing is reduced to nil or negligible proportions by use of a gapped movement ring (34) which has a radially outer screw-thread engaging a cooperating screw-thread in a radially inner surface of the focusing ring. The movement ring (34) is secured against axial and rotational movement relative to the carrier (B) but is biased radially outwardly into positive engagement with the focusing ring. This avoids the need for very precise machining of the screw-threads on the focusing ring (22 ) and movement ring (34).

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a conversion arrangement for mountingoptical units on cameras, particularly though not exclusively on film ortelevision cameras.

When using optical units on modern cameras it is desirable to retain thedesired focusing and iris functions of the optical units.

SUMMARY OF THE INVENTION

The present invention seeks to provide a conversion arrangement formounting optical units on cameras.

Accordingly, the present invention provides a conversion arrangement forcoupling an optical unit to a camera body, the conversion arrangementcomprising:

a mounting means for attachment to the camera body;

a generally cylindrical carrier for attachment to said optical unit,said carrier being coaxially coupled to said mounting means for axialmovement relative thereto:

a focusing ring coaxial with and coupled to said mounting means and saidcarrier for rotation relative thereto wherein rotation of said focusingring causes said carrier to move axially of said mounting means forfocusing said optical unit; and

means biassed into radial engagement with said focusing ring forinhibiting axial movement of said focusing ring relative to said carrierin the absence of rotational movement of said focusing ring relative tosaid carrier, said inhibiting means being operable to control axialmovement of said carrier during rotation of said focusing ring.

Preferably the inhibiting means comprises guide means engaged in ascrew-threaded manner with said focusing ring and secured against axialand rotational movement relative to said carrier so as to guide saidcarrier axially of said focusing ring on rotation of said ring; andwherein said guide means is biased radially of said carrier intopositive screw-threaded engagement with said focusing ring to inhibitaxial movement of said focusing ring relative to said carrier in theabsence of rotational movement of said focusing ring relative to saidcarrier.

BRIEF DESCRIPTION OF THE DRAWING

The present invention is further described hereinafter by way ofexample, with reference to the accompanying drawing which is alongitudinal section through a conversion arrangement according to oneembodiment of the present invention with parts omitted for clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing, this shows a section through a conversionarrangement 10 which is intended for use with a 32 mm Cooke Speed Pancrooptical unit, although it will be appreciated by those skilled in theart that the invention is applicable to other forms of optical units.The conversion arrangement enables the optical unit to be mounted on toa camera such as a film or television camera (having in this example aPL format). The conversion arrangement is fitted within the camera body,which is to the left as seen in the drawing, whilst the optical unit iscontained within the conversion arrangement, facing to the right.

The conversion arrangement 10 comprises a mounting means or member A, acarrier or optical unit support B, a focusing gear C, and an iris drivegear D.

The mounting member A is dimensioned so as to fit on the front of acamera body and has a mounting adaptor 12 of suitable form and amounting body 14. The adaptor 12 engages with the mounting arrangementon the camera to secure the conversion arrangement 10 in position. Themounting body also has an annular recess 18 which opens axially awayfrom the camera body to receive a radially inwardly extending flange 20of a focusing ring 22. The flange 20 is formed at the camera body end ofthe focusing ring 22 and is retained in the recess 18 by the action of athrust ring 24 and retaining ring 26, this being described furtherbelow.

The optical unit support B is co-axially mounted within the mountingmember A so as to be axially slidable relative thereto but is preventedfrom rotating relative to the mounting member A.

An annular extension 28 of the optical unit support B is provided with aradially outer annular groove in which two tenons 30, 32 are located.These support a movement ring 34 which is provided on its radially outersurface with a four start, 14 TPI Whitworth thread. This engages with aco-operating thread formed on a radially inner surface of the focusingring 22. The tenon 30 is secured to the movement ring 34 by means of ascrew (not shown) which passes laterally through the tenon and movementring. The tenon is in turn secured to the annular extension 28 by afurther screw 35, this preventing any rotation of the movement ring 34when the focusing ring 22 is rotated. The movement ring is gapped and,when in engagement with the focusing ring 22 is under compression suchthat it resiles into positive engagement with the focusing ring 22. Themovement ring 34 is positioned so that its gap coincides with theposition of the tenon 32. The latter is not secured to the movement ring34 but serves to support it.

A circlip 36 may be provided under compression in an annular groove in aradially inner surface of the movement ring to assist in urging the ringinto positive engagement with the focusing ring 22. The gap in thecirclip also coincides with the gap in the movement ring 34 to maximizeits effect on the ring.

As will be appreciated, because the optical unit support B is preventedfrom rotating relative to the mounting body 14, rotation of the focusingring 22 screws the movement ring 36 axially of the focusing ring 22,causing the optical unit support B to move axially of the camera bodywhich is secured to the adaptor 12 and mounting body 14. The verypositive engagement of the movement ring 34 with the focusing ring 22avoids any backlash in the relative movement of the focusing ring andthe optical unit support B and therefore in focusing of the opticalunit.

Although the movement ring 34 is illustrated as engaging in arcuategrooves in the tenons 30, 32 the latter could equally engage in groovesor recesses in the movement ring.

The radially inner flange 20 of the focusing ring 22 is maintained inengagement with the mounting body 14 by the thrust ring 24 and retainingring 26. The thrust ring is provided with a gap and has its surfacefacing the retaining ring 26 machined at a preselected angle with theabutting surface of the retaining ring 26 machined at the same angle.This angle lies in the range substantially 55 degrees to 80 degrees andpreferably 70 degrees to the axis of the focusing ring.

The thrust ring 24 is retained between the radial flange 20 of thefocusing ring 22 and the retaining ring 26, the latter being screwedonto a cylindrical extension of the mounting body 14 which forms a wallof the recess 18. Rotation of the focusing ring 22 and therefore theflange 20 causes: the thrust ring to expand very slightly, the abuttingsurfaces of the thrust ring 24 and retaining ring 26 sliding relative toone another. This slight expansion of the thrust ring 24 allows smoothrotation of the focusing ring 22 without introducing any axial play inthe focusing ring 22 relative to the mounting body 14. However, oncerotation ceases, the thrust ring 24 resiles into its rest position, thusproviding a very positive location of the flange 20 and therefore of theoptical unit support B whilst avoiding introducing any backlash betweenthe focusing ring 22 and the mounting body 14 and therefore in focusingof the optical unit. To assist smooth rotation of the focusing ring 22,PTFE washers may be inserted between the flange 20 and thrust ring 24and between the flange 20 and the mounting body 14.

The position of the retaining ring 26 can also be adjusted to providethe desired torque of focusing movement, i.e. light or heavy orsomewhere in between.

It will also be appreciated that the design and operation of the thrustring 24 automatically provides compensation for any wear which mighttake place in the thrust ring itself.

Although the thrust ring 24 is preferably of resilient material, acirclip 40 may conveniently be provided in an annular groove in aradially outer surface of the thrust ring 24 in order to assist inbiasing the latter into firm engagement with the flange 20 and retainingring 26.

The radially inner surface of the flange 20 of the focusing ring 22 ismachined to a close tolerance to bear against the surface of themounting body 14 and prevent any radial play in the ring 22.

In an alternative embodiment, the thrust ring 24 is replaced by aplurality of arcuate segments which are held in a generally circulararrangement by the circlip 40. Each wedge may be provided with a groovein its surface abutting the retaining ring 26 which engages with acorresponding peg or projection on the retaining ring 26 to allow radialmovement of each arcuate segment but to prevent any angular movementabout the axis of the mechanism.

The focusing ring 22 is provided with gear teeth on a radially outersurface to enable the ring to be rotated by the camera focusing drive.

The iris drive gear D is independent of the focusing gear C. Inpractice, the iris actuating mechanism is generally located towards therear of an optical unit. Therefore, since the iris drive is positionedwell into the body of the camera whilst the iris drive gear D is placedtowards the front of the conversion arrangement 10, a remote connectionis required between the two. In addition, because the optical unit inthis example is screwed into the optical unit support and can thereforebe orientated in any position when tightened, some method of radialadjustment is also necessary.

In the drawing, the iris drive gear D has an iris ring 42 and drive pin44 connecting the iris drive gear to the iris actuating mechanism of theoptical unit. The iris ring 42 is coaxially mounted within the opticalunit support B and at its axial end remote from the camera body isformed with a radially outwardly extending flange 46. A generallycylindrical iris carriage 48 is clamped to the flange 46 by means of agenerally cylindrical clamp plate 50. This clamps a radially inwardlydirected flange 52 of the iris carriage 48 against a shoulder on theflange 46 of the iris ring 42. The clamp plate 50 is retained inposition by several screws 54 equi-angularly spaced around the axis ofthe iris carriage 48.

The iris carriage 48 has an axial groove 56 formed in its radially outersurface into which an iris pin 60 locates. The pin 60 is secured to irisgear 62 by means of a bracket 64, the bracket being secured to the irisgear 62 by screws 66. Port holes arranged in the mounting body 14 andoptical unit support B allow access for the bracket 64 to operate theiris carriage 48 and thus the iris in the optical unit, over the fullworking range of the optical unit.

The iris gear 62 is provided on a radially outer surface with gear teethto enable the gear to be rotatably driven by the camera iris drive. Thegear 62 rotates on a closely machined diameter on the mounting body 14,axial displacement of the iris gear being controlled by a circlip 68 atthe rear and a front reice ring 70 at the front.

Rotary movement of the iris gear 62 can therefore be transmitted to theiris of the optical unit via the bracket 64 and iris carriage 48 withoutit being affected by any movement of the focusing ring 22 or movement ofthe optical unit support B.

What I claim is:
 1. A conversion arrangement for coupling an opticalunit to a camera body, the conversion arrangement comprising:a mountingmeans for attachment to the camera body; a generally cylindrical carrierfor attachment to said optical unit, said carrier being coaxiallycoupled to said mounting means for axial movement relative thereto: afocusing ring coaxial with and coupled to said mounting means and saidcarrier for rotation relative thereto wherein rotation of said focusingring causes said carrier to move axially of said mounting means forfocusing said optical unit; and means biased into radial engagement withsaid focusing ring for inhibiting axial movement of said focusing ringrelative to said carrier in the absence of rotational movement of saidfocusing ring relative to said carrier, said inhibiting means beingoperable to control axial movement of said carrier during rotation ofsaid focusing ring.
 2. A conversion arrangement as claimed in claim 1wherein said inhibiting means comprises guide means engaged in ascrew-threaded manner with said focusing ring and secured against axialand rotational movement relative to said carrier so as to guide saidcarrier axially of said focusing ring on rotation of said ring; andwherein said guide means is biased radially of said carrier intopositive screw-threaded engagement with said focusing ring to inhibitaxial movement of said focusing ring relative to said carrier in theabsence of rotational movement of said focusing ring relative to saidcarrier.
 3. A conversion arrangement as claimed in claim 2 wherein saidguide means is a gapped, annular member displaced from its at restposition such that it relies into positive screw-threaded engagementwith said focusing ring.
 4. A conversion arrangement as claimed in claim2 or 3 wherein said guide means has biasing means urging said guidemeans into positive screw-threaded engagement with said focusing ring.5. A conversion arrangement as claimed in claim 4 wherein said biasingmeans is a circlip means coaxial with said guide means.
 6. A conversionarrangement as claimed in claim 2 wherein said guide means has ascrew-thread formed on a radially outer surface thereof engaged with ascrew-thread on a cooperating radially inner surface of said focusingring.
 7. A conversion arrangement as claimed in claim 1 furthercomprising second inhibiting means for inhibiting axial movement of saidfocusing ring relative to said mounting means.
 8. A conversionarrangement as claimed in claim 7 wherein said inhibiting meanscomprises second biasing means for biasing said focusing ring towardssaid mounting means and means for adjusting the force of said bias.
 9. Aconversion arrangement as claimed in claim 8 wherein said adjustingmeans comprises retaining means for axially retaining said secondbiasing means between said retaining means and a portion of saidfocusing ring.
 10. A conversion arrangement as claimed in claim 9wherein said portion of said focusing ring is a radially directedflange.
 11. A conversion arrangement as claimed in claim 8 wherein saidsecond biasing means is displaceable between a first position whereinsaid second biasing means firmly retains said focusing ring againstaxial movement relative to said mounting means and a second positionwherein said bias force is reduced to facilitate rotation of saidfocusing ring whilst retaining said ring against said axial movement;said second biasing means being displaceable from said first position tosaid second position in response to rotation of said focusing ring andfrom said second position to said first position in response tocessation of rotation of said focusing ring.
 12. A conversionarrangement as claimed in claim 11 wherein said second biasing means andsaid retaining means have abutting, wedge-shaped surfaces inclined at apreselected angle to the rotational axis of said focusing ring such thatmovement of said retaining means towards said focusing ring urges saidsecond biasing means radially of said axis against a return force.
 13. Aconversion arrangement as claimed in claim 12 wherein said preselectedangle is in the range of substantially 55° to 80°.
 14. A conversionarrangement as claimed in claim 13 wherein said preselected angle issubstantially 70 degrees to said axis.
 15. A conversion arrangement asclaimed in claim 12 wherein said second biasing means is a gapped ringof a material dimensioned such that said ring resiles radially of saidaxis away from said first and second positions towards a rest position.16. A conversion arrangement as claimed in claim 12 further comprisingcirclip means coaxial with said second biasing means for urging saidsecond biasing means radially of the axis of said focusing ring towardssaid first position.
 17. A conversion arrangement as claimed in claim 12wherein said second biasing means comprises a plurality of arcuatemembers and circlip means coaxial with said arcuate members for urgingsaid members radially of the axis of said focusing ring towards saidfirst position.
 18. A conversion arrangement as claimed in claim 11wherein said first position is radially inwardly of said secondposition.
 19. A conversion arrangement as claimed in claim 1 furthercomprising an iris drive gear coaxial with said mounting means so as tobe rotatable relative thereto for preselecting a desired aperture of aniris of said optical unit, said iris drive gear being connectible to aniris actuating mechanism in said optical unit and an iris drive in saidcamera body to enable actuation of said iris actuating mechanism by saidiris drive.
 20. A conversion arrangement as claimed in claim 19 whereinsaid iris drive gear is connectible to said iris actuating mechanism byway of an iris carriage means coaxially mounted within said carrier formovement axially thereof independently of said carrier; wherein saidiris carriage means has a first portion connectible to said iris drivegear and a second portion connectible to said iris actuating mechanism,and means for adjusting the relative angular positions of said first andsecond portions.
 21. A conversion arrangement as claimed in claim 20wherein said first portion of said iris carriage means comprises an irisring and said second portion comprises an iris carriage coaxial withsaid iris ring, said iris carriage and said iris ring being rotatablerelative to one another, and wherein said iris carriage means hasclamping means for securing said iris carriage and said iris ring in apreselected relative angular position.